1. Field of the Invention
The present invention relates to a liquid crystal display device having a secure fastening and grounding structure, which can improve productivity.
2. Background of the Related Art
Liquid crystal display devices (hereafter called “LCD”) are lightweight, thin, and have low power consumption. Recently LCDs require accelerating improvement in terms of picture quality owing to improvement in the liquid crystal material forming the LCDs, and the development of micron pixel forming technologies. These advances have gradually widened the range of applications ranges of the LCDs.
In general, a liquid crystal module (hereafter called as “LCM”) is provided with a liquid crystal display panel. The liquid crystal display panel contains liquid crystal injected between upper and lower glass substrates, a polarizing plates at upper and lower surfaces of the liquid crystal panel for polarizing light transmitted therethrough, and a backlight unit. The backlight unit has a light source and a light plate for supplying light to the liquid crystal display panel. The LCM receives a picture signal from outside the LCM and displays the picture signal thereon.
driving the LCM, and a system case.
FIG. 1 illustrates a perspective disassembled view of a related art LCM, and FIGS. 2A and 2B illustrate a ground structure of a related art LCD. FIG. 2A illustrates a front enlarged view of an LCM, and FIG. 2B illustrates a back enlarged view of the LCM.
Referring to FIG. 1, a related art LCM 10 has a backlight portion 12, and a liquid crystal panel 11, both supported on a support main 13 and a top case 20.
There is a cover bottom 14 on an inside bottom of the support main 13, and there is a backlight portion 12 on the cover bottom 14, having a reflective plate 12a, a light plate 12b, a spreading, or protective sheet 12c, a first prism sheet 12d, a second prism sheet 12e, a spreading or protection sheet 12f, and a lamp 25. The liquid crystal panel 11 is placed on the backlight portion 12.
The lamp 25, at one side of the support main 13, emits light, and there is a lamp housing (not shown) around the lamp 25 for protection of the lamp 25, and reflecting the light.
In the meantime, there is a top case 20 of metal over the liquid crystal panel 11, fastened to underlying support main 13, to hold the liquid crystal panel 11, and the backlight unit 12.
The cover bottom 14 of metal at a side of the support main 13 serves as a heat discharging plate for dissipating and discharging heat from the light source to an outside of the LCD, as well as reinforcement of a bottom supporting structure for prevention of distortion of the LCM 10 by an external force applied to the LCM 10. The cover bottom 14 also supports the light plate 12b and various sheets 12.
In the meantime, there is a printed circuit board (hereafter called as “PCB”) and the like under the support main 13, a back side of the LCM 10. The PCB 30 has a Drive Integrated Circuit (hereafter called as “D-IC”) mounted thereon for driving switching devices (i.e., WT array) of the LCM 10. The LCM 10 and the PCB 30 are electrically connected with a Tape Carrier Package (hereafter called as “TCP”) 31 for transmitting control signals and video signals from the D-IC to the LCM 10. The PCB 30 is connected to the liquid crystal panel 11 with the TCP 31, and in general in close contact with a back side surface of the support main 13 when the PCB 30 is mounted inside of the liquid crystal display device. For putting the PCB 30 on the back side surface of the support main 13, the TCP 31 is folded to a back side from a state extended in a lateral direction.
If is required, the liquid crystal device is provided with a ground structure for preventing defective system operation or distortion of a picture caused by Electro-Magnetic Interference (hereafter called as “EMI”).
In general, a driving circuit of the LCD is influenced by electromagnetic waves. Particularly, since the PCB 30 has devices, such as a power supplying circuit, and switching devices, to induce an inductive voltage caused by external static induction and electromagnetic induction, it is required that conductive components of the LCD are grounded without fail for preventing this.
For this, it is required that the PCB 30 is grounded to the top case 20, and the top case 20 is electrically connected to a ground structure of a system external case, for securing stable operation of the PCB. Moreover, it is also required that the lamp housing that surrounds the lamp 25 is grounded.
FIG. 2A illustrates a front surface of the LCM 10, having a projection from each corner. The projection 20a is used as a screw fastening portion for fastening the LCM 10 to a system case by a front mounting method.
That is, the projection 20a has a plurality of screw fastening holes 21a, and 21b. The fastening holes 21a are for fastening the LCM 10 itself and the fastening holes 21b are for fastening the LCM 10 to the system case. One of each of the fastening holes 21a for fastening the LCM 10 itself is in each of the projections in upper and lower portions of a right side of the LCM 10.
FIG. 2B illustrates a back side of the LCM 10. Also, in the back side of the LCM 10, the LCM 10 itself is fastened with screws. According to this, the LCM 10 has screw fastening holes 22a, 22b, 22c, 22d, and 22e, in corners and a central portion. Referring to FIG. 2B, the LCM 10 has five screw fastening holes 22a, 22b, 22c, 22d, and 22e in total in the back side surface of the LCM 10.
The screw fastening holes in the front and back surfaces fasten the LCM 10 itself, and the screws fastened to the screw fastening holes ground the PCB 30.
There are structures 23 for grounding the PCB 30 to the cover bottom 14, and the screws for fastening the LCM 10 itself ground the cover bottom 14 to the lamp housing and the top case 20. Accordingly, by screwing the screws into the fastening holes in the LCM 10, the LCM 10 itself is fastened, and the grounding structure is completed.
However, the related art LCD has the following problems.
First, the cost for many screws and the time required for fastening these screws due to many screw fastening holes in the related art reduces productivity.
Second, the foreign material formed during making many screw holes reduces the secure productivity of the LCM itself.
Third, there are intermittent discontinuities in the grounding contact surfaces between the top case and the cover bottom in the projections at a side of the LCM of the related art caused by assembly tolerance. This causes the contact surfaces to fail to eliminate the influence of noise coming from the electromagnetic wave.